Build/Test Tools: Add sys_get_temp_dir() to open_basedir tests.

In PHPUnit 10.3.5, 9.6.13 and 8.5.34, the child processes used for process isolation now use temporary files to communicate their result to the parent process.

This caused a failure in some tests that set the `open_basedir` PHP directive to a value that did not include `sys_get_temp_dir()`.

This adds `sys_get_temp_dir()` to the `open_basedir` value set by the tests to ensure that permission is still granted for the temporary directory.

PHPUnit uses `sys_get_temp_dir()`. To ensure the result is the same, Core's `get_temp_dir()` function is not used.

References:
- sebastianbergmann/phpunit#5356

Props desrosj, mukesh27, SergeyBiryukov, costdev.
Merges [56622] to the 6.3 branch.
See #59394.

git-svn-id: https://develop.svn.wordpress.org/branches/6.3@56624 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/tests/admin/wpAutomaticUpdater.php

@@ -610,7 +610,7 @@ public function test_is_allowed_dir_should_return_true_if_open_basedir_is_set_an
 
  $open_basedir_backup = ini_get( 'open_basedir' );
  // Allow access to the directory one level above the repository.
- ini_set( 'open_basedir', wp_normalize_path( $abspath_grandparent ) );
+ ini_set( 'open_basedir', sys_get_temp_dir() . PATH_SEPARATOR . wp_normalize_path( $abspath_grandparent ) );
 
  // Checking an allowed directory should succeed.
  $actual = self::$updater->is_allowed_dir( wp_normalize_path( ABSPATH ) );
@@ -645,7 +645,7 @@ public function test_is_allowed_dir_should_return_false_if_open_basedir_is_set_a
 
  $open_basedir_backup = ini_get( 'open_basedir' );
  // Allow access to the directory one level above the repository.
- ini_set( 'open_basedir', wp_normalize_path( $abspath_grandparent ) );
+ ini_set( 'open_basedir', sys_get_temp_dir() . PATH_SEPARATOR . wp_normalize_path( $abspath_grandparent ) );
 
  // Checking a directory not within the allowed path should trigger an `open_basedir` warning.
  $actual = self::$updater->is_allowed_dir( '/.git' );